Vasoactive intestinal polypeptide in the pituitary pars nervosa

Area of Science:

• Neuroendocrinology
• Neuropeptide research
• Pituitary gland function

Background:

• Vasoactive intestinal polypeptide (VIP) is a neuropeptide found in the hypothalamus and hypothalamo-hypophyseal portal blood.
• Recent discoveries indicate VIP's presence in the central nervous system, prompting further investigation into its role in neuroendocrine regulation.

Purpose of the Study:

• To investigate the presence and localization of VIP in the pituitary gland of various mammalian species.
• To determine the potential role of VIP in neurohypophyseal hormone regulation, specifically vasopressin release.

Main Methods:

• Immunocytochemistry was employed to visualize VIP.
• Radioimmunoassay was utilized to quantify VIP levels.
• Studies were conducted on pituitary tissues from several mammalian species, with a focus on the dog.

Main Results:

• Significant quantities of VIP (100-250 fmol/mg) were detected in the pituitary pars nervosa across multiple mammalian species.
• In dogs, VIP was identified within nerve fibers in the pars nervosa.
• VIP concentrations were quantified using radioimmunoassay.

Conclusions:

• The pars nervosa of the pituitary gland is a site of considerable VIP concentration in mammals.
• VIP in the neurohypophysis, particularly in nerve fibers, may function as a local releasing agent for vasopressin.
• These findings suggest a novel regulatory pathway for vasopressin secretion involving VIP.